I have already found your Catalogue of Nebulæ in zones, very useful in my twenty-foot sweeps, and I mean to get it in order for publication by degrees; but it will take a long time, as it will require a great deal of calculation to render it available as a work of reference. The permission to examine Leibnitz’s MSS. will be very acceptable to me should I again visit Hanover, but of that I have no immediate prospect. A very intimate friend of mine, Mr. James Grahame, talks of taking up his residence at Göttingen for the sake of the library of the University. He is writing a history of America. I shall give him a letter to Professor Blumenbach, and shall beg you to introduce him to his son, Regierungsrath B., and perhaps Dr. Groskopf will make him acquainted with Dr. Koch, of the Royal Library at Hanover, who may be able to assist him in his researches.... If there is anything in England you wish for, or that you cannot get so well in Hanover, pray name it, and I will make a point of procuring it.... J. F. W. HERSCHEL TO MISS HERSCHEL. DEVONSHIRE STREET, _Dec. 30, 1825_. * * * * * I have not been doing much in the astronomical way of late—but, _en revanche_, Mr. South has been hard at work, and has sent a second paper of 460 double stars to the Royal Society. He is returned from Paris, and is now busy erecting an observatory, as he means to stay six months in England, and cannot be so long without star-gazing. I enclose a little thing which I published in Schumacher’s _Astronomische Nachrichten_ which may interest you. Shortly I shall have the pleasure to transmit you some papers on the longitude of Paris, and on the parallax of the fixed stars, which I have now in hand. Do not suppose that I pretend to have discovered parallax, but if it exists to a sensible amount, I think it cannot long remain undiscovered if anybody can be found to put into execution the method I am about to propose, and I hope it will be taken up by astronomers in general. I have so far perfected the system of sweeping with the twenty-foot that I can now make sure of the polar distances of objects to within 1ʹ, and their right ascensions to certainly within 2ʺ of time. I have re-observed a great many of the nebulæ, and in the course of the few sweeps I have made, have discovered many not in your most useful catalogue. But I am now fixed in town for the winter, and have brought up the said catalogue to consider of the best mode of preparing it for publication, if it meets with your approbation. Mr. South’s later observations strikingly confirm the results obtained by us jointly respecting the revolving stars, and afford new and very remarkable instances in support of my father’s ideas on this subject. Of one pair (the double star ξ Ursa Majoris) I have no doubt we shall soon obtain elliptic elements. [Sidenote: 1825. _Letter from Professor Gauss._]